Cait's whole story is about whether she actually wants to serve in the temple or follow her sister(who didn't want to serve in the temple). Building the temple here is enforcing that she shouldn't follow her sister. It's not inherently corrupt but It's bad if you want to support her desire to be free.
I mean, that's one way of looking at it. Alternatively, Cait
wants to serve Mallach, and supporting her plan to build a temple means she gets to do so under her own terms. She gets to build a safe place free of politicking where she can do the work that matters to her. It doesn't preclude her from exploring, but... there's more than one kind of adventure in life. She does tell you that she loved temple life and leaving the temple to go travelling was a very difficult choice for her.
Also, if I got it right -- Cait would be required to have a child as the priestess, which she seems to be not the biggest fan of, considering she is one of few ladies with self conscious to not jump into unplanned/early motherhood.
I don't see that she'd be required to have a child. She talks about there being different roles within a temple, and about consent being all important. As for not wanting to be a parent, 'not now' doesn't mean 'never'. I didn't get a vibe that she'd never consider having a child.
The only issue I see is in Barney wanting to make his daughters his heirs - probably not practical for Cait if she's a temple matron hundreds of miles for Jassira. But I can see an ending where a rescued Calla takes on the role of Jassiran noble, travelling around like Barney does, while Cait finds her own path in life planting her temple in the Marches. If the champ visits Jassira and opens some waystones there, they could then help the sisters stay in close contact.